Applied Mechanics and Materials Vols. 672-674

Abstract: Firstly, this paper introduces the development of new materials, new technology and new manufacture in power industry of China, energy-saving, low noise and smart distribution transformers are widely used in countryside power grid reconstruction. In this paper, application status and development trend of different types of distribution transformers were introduced and compared in terms of new material and new structure, such as oil-immersed distribution transformer, amorphous core transformer(AMT), dry-type transformer, SF6 insulated distribution transformer, composite transformer and other types of distribution transformers. The development of distribution transformer is mainly based on energy saving, miniaturization, wound core and amorphous alloy nowadays, but the class-H dry-type transformer and tridimensional toroidal-core amorphous alloy transformer are the future direction of development. The technology application of smart distribution grid, power electronics technology and dynamic reactive power compensation technique will also affect the safety and economic operation of distribution transformer.

Abstract: An improved Charge Simulation Method (CSM) is proposed in this paper. Based on this method, the model of the overall 500kV substation is established, and then the power frequency electric field in substation at the height of the 1.5mabovethegroundis simulated and calculated. Specifically, these on 500kV switch yard in the station are simulated and analysis. The results show that the simulation results are in good agreement with the actual substation measured results, which is proved the correctness of the model and the algorithm. This paper provides an effective method for the rapid analysis of the distribution of power frequency electric field in ultra-high-voltage substation, and also can use the method to study the effects of electric field distribution factors in substation.

Abstract: In this paper, a simulation model for the propagation of transformer PD pulse has been constructed,and the propagation of PD in a real substation were investigated. We also studied the frequency characteristics of currents at different detection positions, and the influences of substation network are analyzed in aspects of system resonant frequency. The optimal detection position and the optimal measuring band are proposed. The results show that, the calculated range of substation network and capacitive apparatus play the key roles in impedance characteristics.

Abstract: Short-circuit withstand capability test of transformers is mechanical strength withstand test under strong current imposed on power transformers, which is a kind of assessment method of comprehensive technical capabilities and technological level of transformer manufacturing. This paper analyzes the theory basis of short-circuit withstand capability test and calculates the imposed short-circuit current value and provides experimental scheme which is verified by the testing. All is to verify the ability to withstand a short circuit of 110kV power transformer.

Abstract: A partial discharge (PD) on-line monitoring and positioning system for high-voltage cables based on double-ended testing technology is developed. The hardware of this system includes a high-frequency current sensor, site PD signal acquisition and PD monitoring server. In order to achieve real-time monitoring and remote diagnostics of the XLPE cable partial discharge status, the designed software system is divided into front-end control system and remote diagnostic system. And finally, the correctness and effectiveness of the system is verified by XLPE cable partial discharge testing.

Abstract: This paper focuses on an experimental investigation of the arc plasma behavior in current breaking process of a certain type of 12kV ring network cabinet’s SF₆ load switch. From the frames obtained by high-speed photography, the characteristic of the arc movement was revealed. According to analysis, the structure of load switch was optimized and its breaking capacity about transfer current was improved. This study may provide a reference for design and optimization of load switches.

Abstract: With the continuous development of HVDC technology, the increase in the number of ports in the MTDC system and the increasing complexity of network topology, the deficiency of traditional flow calculation method is becoming clear. In this paper, a power flow calculation method that contains distribution of VSC-MTDC mixed system which based on asynchronous iterative method is put forward. On the basis of the current model converter, by dividing the hybrid system and coordinating calculation of boundary variables, this method achieves the global convergence of the whole system. The shortcomings that numerous converter stations in VSC-MTDC power flow method, slow operations and poor convergence in communication network with large number of nodes, are overcome in this method. Moreover, more control modes in the operation of the converter station are considered. Finally, through the example, the correctness and effectiveness of this method are verified.

Abstract: Converter transformer is one of the most important equipments of UHVDC power transmission system, its faults directly affects the safe and stable operation of DC system. The valve winding of converter transformer needs to withstand the voltage that consist of DC voltage and serious distortion of AC voltages (harmonic bound) which are similar to the AC sine waveform compound voltage, so in the design and manufacture of the valve side of converter transformer, bushing is much more complex and difficult than alternating current casing.Valve bushing is weak spot of converter transformer insulation. Through the anatomy of failure bushing, the reason of bushing failure is analyzed. Without changing body size of the converter transformer, the bushing of new structure is developed and the old bushing is replaced to improve the reliability of equipment operation.

Abstract: This paper introduced the basic principle of dielectrophoresis.The DEP microchip was classified according to the modes of electrical sources. It analyzed and compared the advantages and disadvantages of the interdigitated electrodes, parabolic electrodes, fort electrode and three-dimensional electrode.The paper also introduced the fabrication process of chip and cell analytic application recently. In the end its application prospect and development direction.was conducted .

Abstract: The paper briefly introduces the structure principle and excellent characteristics of protograph LDPC codes and designs the serial encoding circuit based on FPGA. On the basis of the further study of Belief Propagation (BP) algorithm, λ-min algorithm and A - min algorithm, decoder is designed adopting the complexity and performance eclectic mixed decoding algorithm. Meanwhile, it is verified by the simulation. The result shows that coding gain can be up to about 6 to 8 db, if it meets the requirements of 10^-5 bit error rate.